Within the field of packaging of pourable products, and in particular of pourable foods, there are various kinds of packaging containers used. The packaging containers vary in package shape, packaging material, etc. resulting in variation in the method used for filling of the packaging container and sealing of the packaging container. The present invention may preferably be used for a packaging container made from a packaging laminate comprising a core layer and several surrounding barrier layers.
When sealing an end of a tubular packaging container use is often made of sealing jaws, clamping and heating the end of the packaging container in order to seal one end thereof. The basic technique is well-known and will not be discussed in any more detail here. For the purposes of the present invention, however it should be mentioned that “tubular” includes packages having a cross section other than circular, such as quadratic, rectangular, hexagonal, oval, etc, i.e. a packaging container being formed by bonding two opposite edges thereof to form a sleeve.
The sealing of an end of a packaging container is a complex procedure. The end should be sealed, formed and folded according to a preset pattern, and fixed to the desired shape (usually flat in the case of the bottom of a container). The different operations are not necessarily performed in the order stated above; when sealing the final open end of a container, the sealing should preferably be performed late, since a surplus of air will be caught inside the container if sealed too early. This poses no problem when the first end of the container is sealed, formed and folded.
The stated operations are not necessarily performed by the same tool, either. Generally, the sealing and initial forming and folding are performed by one tool, and the final folding and fixing is accomplished by another tool, or arrangement of tools.
The tool for sealing and initial forming and folding may comprise two opposing sealing jaws, clamping the open end of the tubular packaging container and providing energy for the accomplishment of sealing. On their way from an open position to a clamping position the two opposing sealing jaws may follow a path of movement such that they initiate the forming and folding, and after clamping and sealing the packaging container, they may continue their movement to continue the forming and folding. Even if the path as such may be simple enough, the mechanics needed in order to make the sealing jaws follow such path will be more complex, in particular since factors such as reliability, repeatability, and durability are important and since price is always an issue. Examples of prior art solutions may be found in WO2004054790, by the present applicant, and US2008/0276576 also by the present applicant.
The present invention aims at providing a bottom form and sealing unit which is easy to operate, durable and reliable.